Fluid sometimes needs to be drained from a body. For example, urine formed in one or both kidneys might need to be drained into the bladder. One way to accomplish such drainage is to use a medical device that conveys the fluid (e.g., urine) through a lumen. Such devices include stents and catheters. Existing stents can be uncomfortable for the patient, especially when they reside in the ureter between the kidney and the bladder, can be difficult for a medical professional to place in a patient, or can allow urine from the bladder to move into the ureter towards the kidney.